When examining persons by means of x-ray, especially for mammography, the person and the operator are usually exposed to scattered and reflected x-rays.
FIG. 1 is a schematic side view of a digital mammography apparatus 10 comprising a radiation source 11, a collimator 12 and a detector assembly 13. The breast 14, to be examined is pressed to and flattened between the paddles containing the collimator and detector assembly. The x-rays 15 from the source 11 are collimated by the collimator 12 and pass through the breast 14 and heat the detector assembly. However, some of the x-ray incident to the collimator is reflected and scattered. The scattered/reflected beams are denoted with number 16. These beams are scattered in all direction, here also into the plane of the drawing and out of the plane of the drawing (not shown). There are also some rays that scatter from the source 11.
The undesired radiation can be up to 1 m/Gray, and usually occur between the x-ray source and the collimator. Thus, the there may occur two different radiation strengths: one before the collimator and one after the collimator. The radiation is stronger before the collimator, and the person to be examined must be protected.
Prior art disclose different arrangements for protecting a person at mammography  examination. For example U.S. Pat. No. 4,090,084 relates to a mammography apparatus and more particularly to the means for compressing a pressure plate of the apparatus against the breast. The mounting of the pressure plate is such that the pressure can be applied uniformly throughout the breast area. To enable such uniform pressure to be obtained, the pressure plate is connected at its opposite ends to slide means which slide on tracks mounted on the cone of the X-ray machine. For the determination of the thickness of the compressed breast tissue between the pressure plate and the film upon which the breast rests, a measuring rod is secured to the tracks and a pointer is attached to the means which move on the tracks.
In this case, the collimator is an oblong, conical unit, which extends from the x-ray source to pressure plates. Thus, the collimator is not displaceable. The pressure plate is displaceable and the shield is arranged as a part of the pressure plate.
Another arrangement is disclosed in U.S. Pat. No. 4,122,350, according to which an adjustable collimator is provided for use in mammography in which there is a mounting ring for securing the collimator to an x-ray source; a collimating cone having a plurality of leaves, each pivotably secured at one end thereof to said mounting ring and positioned in overlapping relationship to one another to define at their opposite ends a substantially kidney shaped opening through which x-rays may be directed to a female breast positioned below said cone; and a collar positioned about and capturing the plurality of leaves and to be raised and lowered along the leaves relative to said mounting ring to adjust the size of the opening.
This document describes an adjustable collimator extending from the x-ray source to a supporting plate. The collimator, by means of a displaceable collar, can be adjusted to direct the x-rays to a female breast. No particular radiation shields are used. However, a non-conductive sheet (S) draped from the collimator and is placed between the collimator and the breast to protect the breast from contacting the collimator.